The effect of AZT and interferon on the replication of HIV-1 was evaluated by PCR. Briefly, H9 and U937 cells were infected with cell-free HIV-1, after which the drugs were added at the indicated concentrations. AZT 50 ug/ml, rlFNa at 50U/ml or in combination at the same concentrations. Genomic DNA and RNA were analyzed by PCR using primers to the gag region (SK 38/39). Virus production was measured by reverse transcriptase (RT) and p24 antigen assays. Greater than 95% inhibition of HIV replication was observed with AZT and the combination of AZT and rlFNa from 3-4 days after infection using the p24 and RT assays in both the H9 and U937 cells. Viral DNA and RNA synthesis were not significantly inhibited by rlFNa. Some inhibition of DNA and RNA was observed with AZT alone followed by a recovery of viral nucleic acid with time. More than 80% inhibition of viral DNA synthesis was observed with the combination of AZT and rlFNa. Viral RNA was undetectable in both infected H9 and U937 cells in the presence of AZT and rlFNa combined. Our results indicated that combination therapy with AZT and rlFNa may be more effective for sustained inhibition of virus replication at all levels. DDC was similarly evaluated using infected H9 and U937 cells. Treatment with concentrations of 0.5 and 1 uM resulted in greater than 95% inhibition of HIV DNA in both target cells. Quantitative PCR may be a useful way to evaluate the antiviral activity of specific drugs in vitro. Other antiviral therapies that are currently in clinical protocols, such as the combination of ddC and rlFNa, ddC and AZT and ddl alone are also being evaluated in these 2 cell systems using additional strains of virus, such as the MN and AZT resistant strains. The molecular mechanism of this inhibitory effect will be studied by analyzing the expression of various host genes in response to drug treatment. In other studies, the activity of aurin tricarboxylic acid (ATA) and its analogs were analyzed by PCR. Several species of alpha interferons were evaluated for their anti-HIV activity in H9 and U937 cells. In other experiments, inhibitors of ODC, tyrosine kinase, divalent metal chelators, integrase, protease and RT and DNA primase and gyrase inhibitors are being evaluated in vitro for anti-HIV activity.